In the electrolytic refining of copper, the copper at relatively high purity is electrodeposited on cathodes in electrolytic cells from the electrolyte by a process which can be generally referred to as electrorefining.
The electrolysis is effected by direct current which can be delivered to the cathodes by cathode-carrier bars affixed to the cathode plates and forming hangers which can rest upon current-carrying rails which constitute busbars. Similar large cross-section rails or bars serve to distribute the electric current to a number of cells and within the electrorefining plant.
Experience has shown that it is desirable to maintain a substantially constant current supply to each cell and a substantially uniform or constant current distribution to all of the cells of the apparatus and that problems are encountered when the current distribution is not uniform. Uniform current distribution is essential for optimum electrical energy utilization, to minimize the specific current consumption and to ensure the production of high quality cathodes and concomitantly high purity copper.
Experience has also shown that the uniformity of the current distribution can be adversely affected in a number of ways. For example, a short circuit between cathode and anode in one cell, or the formation of a high resistance path at a contact region between the cathode and the current supply network, are just two of the several ways in which the uniformity of the current distribution can be endangered.
It is, therefore, a common practice to provide means for monitoring the current flow to one or more or all cells, such means generally comprising a galvanometer and like mechanical measuring devices which are calibrated in terms of current amplitude.
Such devices are of comparatively simple construction although experience has shown them to be highly inaccurate and unreliable.
For example, different instruments must be calibrated repeatedly and continuously and even then may not be fully reliable.
It has been difficult with such instruments to rapidly and quantitatively evaluate short circuits and bad contacts.
Efforts have been made to use thermocolor transformation techniques, comparatively labor-intensive approaches, temperature measurements for infra-red cameras on, for example, the cranes provided in the plant, e.g. for transferring the cathodes. The latter approach has been associated with high investment and capital costs.